【作者】 安宗裕；

【导师】 汪泉弟；

【作者基本信息】 重庆大学 ， 电气工程， 2014， 博士

【摘要】 混合动力汽车相比传统汽车电磁兼容(Electromagnetic Compatibility, EMC)问题更加突出，其车载大功率电力电子设备产生的强烈电磁干扰(ElectromagneticInterference, EMI)会对自身系统和车内其它系统造成干扰影响。为了解决混合动力汽车大功率电力电子系统的EMC问题，本文重点研究车载大功率直流电源变换器系统EMC问题，掌握该系统的EMI测量方法、产生机理、传播路径、预测模型和优化方案，本文的研究思路和方法可以推广到解决车载其它EMC问题较突出的系统研究中，能够为混合动力汽车EMC问题研究提供理论和实践指导。论文主要研究内容及取得的成果有：1）采用消耗型铁氧体磁环对直流电源变换系统线束EMI进行排查，对多个线束上的EMI信号进行独立测量，获得直流电源变换系统单独产生的EMI水平。采用小波变换分解EMI信号并提取对应的小波系数，基于各分解尺度下的小波系数计算出了干扰信号频域内的三种特征参数：累积能量参数、突变参数和不平衡参数，该特征参数能够表征时域EMI信号的频域特征。2）通过对直流电源变换器系统EMI产生机理分析，建立了产生干扰振荡波形的等效电路模型，并推导出振荡波形的数学表达式，该数学模型能够表征干扰波形的主要特征。在EMI传播路径研究过程中，依据变压器主电路中变压器的结构和初次级线圈之间寄生电容的分布，建立了EMI通过变压器的耦合路径模型。推导出了EMI从初级绕组耦合到次级绕组的机理，并定性分析出降低EMI耦合作用的三种方法。3）建立了直流电源变换器系统传导EMI预测模型，包含的子模块主要为：基于传输线理论的电缆模型、基于多软件联合仿真计算的变压器和带铁芯电感的“实体-场-路”模型、干扰源的集中等效模型、基于静电场有限元方法的寄生电容计算模型。将各个模块的模型集合成系统仿真模型，仿真计算得到系统的传导EMI水平，并通过实验对比验证了该系统EMI预测模型的准确性。4）基于直流电源变换器系统差模和共模EMI传播路径，分别建立其等效电路模型，分析得出功率器件对机壳的寄生电容是影响系统共模EMI水平的重要因素，提出通过改变寄生电容大小的方法来改善系统EMI。通过仿真分析增大功率器件导热片与散热器之间导热硅脂的填充厚度，减小导热片与散热器之间导热硅脂的介电常数，以及减小功率模块导热片的面积这三种优化方法，能够有效地降低系统共模EMI水平，并根据实验条件验证了前两种优化方法在低频段抑制传导EMI的正确性和有效性。5）设计研究了电源变换器系统EMI滤波器。通过测量直流电源变换器系统干扰源内阻抗和电源线EMI水平，建立滤波器的高频等效电路模型并提取参数，通过对滤波器插入损耗的仿真验证了滤波器的有效性，并将设计制作的滤波器加入直流电源变换器系统进行滤波效果验证，实验结果表明本文所设计的EMI滤波器能够有效地抑制变换器系统电源线上的传导EMI水平，并且弥补了导热硅脂只能抑制低频EMI的缺陷。更多还原

【Abstract】 Compared with traditional vehicles, hybrid electric vehicles have obvious EMC(Electromagnetic Compatibility) problems. The high-power electronic devices onvehicle will bring about strong EMI (Electromagnetic Interference), which willnegatively interference these devices and other systems on the same vehicle. In order tosolve the EMC problems of high-power electronics devices of hybrid electric vehicles,this dissertation mainly focuses on the EMC problem of high-power DC/DC converter,studying the EMI measurement methods of this system, mechanism of EMI production,EMI transmission routes, EMI predictive model and optimal schemes. The research ideaand approach of this dissertation can be applied to other on-vehicle systems with seriousEMC problems, thus offering theoretical and practical guide to EMC problems ofhybrid electric vehicles. The main research contents and results of this dissertation arelisted as follows.1) Consumable ferrite is employed to investigate EMI of DC/DC converter lines,so that EMI signals of multiple lines can be independently measured and the separateEMI levels of DC/DC converter lines can be obtained. Also, wavelet analysis is appliedto decompose EMI signals and to obtain corresponding wavelet coefficients. Based onwavelet coefficients on each decomposition scale, three characteristic parameters ofEMI signal in frequency-domain can be calculated, including cumulative energyparameter, mutation parameter and unbalance parameter.2) Based on the EMI production mechanism of DC/DC converter system, anequivalent circuit model producing EMI vibration wave is constructed. This model canrepresent main properties of EMI wave, and the mathematic equation of vibration wavecan be deduced. In the study of EMI transmission routes, a model that describes theEMI coupling route through the transformer is established on the basis of transformer’smain structure and the distribution of parasitic capacitance between the primary andsecondary coils. From this model, the mechanism of EMI coupling from primarywindings to secondary windings has been studied, and three approaches to reduce EMIcoupling effect have been qualitatively analyzed.3) A conducted EMI predictive model of DC/DC converter has been constructed.This model actually is consist of many sub-models, including cable model based ontheory of transmission lines,“object-field-circuit” model of transformer and iron-core inductor based on multiple-software simulation, and parasitic capacitance calculationmodel based on the finite element method of electrostatic field. All these sub-models areintegrated to form a system model, and conducted EMI level has been calculated by thisintegrated system model. The accuracy of this system EMI predictive model has beenverified via practical test comparison.4) According to the different EMI transmission paths of DC/DC converter system,the CM equivalent circuit and the DM equivalent circuit are separately constructed. It isconcluded that parasitic capacitance between power components and chassis is animportant factor to affect the CM EMI level of this system. Therefore, a new approachchanging parasitic capacitance has been proposed to reduce EMI. In simulation, thereare3optimal methods to reduce system CM EMI, namely increasing thickness ofthermal conductive adhesive between heat sink and heat-conducting plate of powercomponents, decreasing the permittivity of thermal conductive adhesive and decreasingthe geometry shapes of heat sink on power electronics modules. According the labcondition, the validity and effectiveness of the first two optimal methods have beenverified.5) The design process of EMI filter of DC/DC converter has been studied. Aftermeasuring interference source impedance of DC/DC converter system and EMI levelsof power lines, a high-frequency equivalent circuit of EMI filter has been constructed,and necessary parameters have been extracted. The effectiveness of filters is verified viasimulation of insertion loss. Meanwhile, the designed EMI filters are applied to DC/DCconverter system to verify their filtering performance, and the result shows thesedesigned filters can effectively suppress the conducted EMI level on power lines ofDC/DC converter system.更多还原